That's not how it works! See, what you do is change the way the game is displayed, so it was as if you were going to TATE it-- but don't physically turn the screen. Then tweak the directional settings:
Right = Up Key
Left = Down Key
Up = Right Key
Down = Left Key
This will make it so you can control the game as if it were a hori shmup!
As an alternative, you can play Progear in vert mode too
